Before we dive into the download process, make sure you have the following:
The safest way to download the ISO is directly from Microsoft. While they have made it slightly harder to find compared to newer versions, the files are still hosted on their servers. windows 8.1 pro iso 64 bit download
Once downloaded, verify that the file size is roughly 3.5 GB to 4.5 GB (depending on the specific version and updates included). A file significantly smaller than this is likely corrupt or incomplete. Before we dive into the download process, make